Optical clearing is a new technique that improves 3D imaging of the enteric nervous system (ENS). Researchers used optical clearing and confocal microscopy to image the human ileum in 3D. Optical clearing reduced light scattering in the tissue, allowing deeper photon penetration and higher definition images. This generated a panoramic 3D view of gut wall structures like nerves, muscles, and crypts. The researchers plan to use this method to study gastrointestinal disease mechanisms by observing microstructures, vasculature, and nerve networks in animal models and comparing healthy and diseased human tissues.

1. RESEARCH HIGHLIGHTS
Nature Reviews Gastroenterology & Hepatology 8, 600 (2011); published online 4 October 2011; doi:10.1038/nrgastro.2011.167
NEUROGASTROENTEROLOGY
Improving 3D imaging of the enteric nervous system
Imaging the enteric nervous system
(ENS)—a complex multidimensional
structure comprising dispersed neurites
and fibers and structural components
—is challenging. Shiue-Cheng Tang and
colleagues now show that optical clearing
could aid 3D visualization of the ENS.
Conventional microtome-based 2D
ENS imaging provides only a limited
perspective of the neural network. To
generate a comprehensive 3D view,
Liu et al. imaged the human ileum using
confocal microscopy after optical clearing.
“Optical clearing reduces light scattering
in the specimen, thus promoting photon
penetration across the tissue to generate
high-definition images,” explains Tang.
Human ileal enteric nerve specimens
were immunostained with marker PGP9.5
and immersed in optical-clearing solution
before deep-tissue confocal microscopy;
images were then processed for 3D image
rendering and analysis.
Fluorescence signal decay along the
focal path in the human ileal wall was
3D projection of human neural tissue. Courtesy of
S.-C. Tang.
reduced in optically-cleared tissues
compared with control (saline-immersed)
tissues. Indeed, immunostaining
signal strength rapidly declined over a
penetration depth of 65 μm in control
tissue, whereas signal strength slowly
decreased in optically-cleared tissue at
depths of 65–150 μm. Optical clearing
also increased the signal-to-noise ratio
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(a measure of the ability to distinguish
the target from the background). Digital
analysis of high signal-to-noise ratio
images allowed the identification of
nerve fibers and quantification of signal
peaks. Stacking these images created
a “panoramic 3D view of the gut wall
innervations and microstructures
including circular and longitudinal
muscles and crypts,” says Tang.
The researchers now plan to “develop
labeling and imaging methods for
observing the gut tissue microstructure,
vasculature and innervation networks
to study gastrointestinal disease echanisms
in animal models ... and to compare healthy
and diseased tissues in clinical research.”
Katherine Smith
Original article Liu, Y. A. et al. Optical clearing improves the
imaging depth and signal-to-noise ratio for digital analysis
and three-dimensional projection of the human enteric
nervous system. Neurogastroenterol. Motil. 23, e446–e457
(2011)
VOLUME 8 | NOVEMBER 2011